CN106001978B - Lead-free solder alloy, electronic circuit board, and electronic control device - Google Patents
Lead-free solder alloy, electronic circuit board, and electronic control device Download PDFInfo
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- CN106001978B CN106001978B CN201610154029.4A CN201610154029A CN106001978B CN 106001978 B CN106001978 B CN 106001978B CN 201610154029 A CN201610154029 A CN 201610154029A CN 106001978 B CN106001978 B CN 106001978B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400 degrees C
- B23K35/262—Sn as the principal constituent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
- B23K35/0244—Powders, particles or spheres; Preforms made therefrom
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
- B23K35/0244—Powders, particles or spheres; Preforms made therefrom
- B23K35/025—Pastes, creams, slurries
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C13/00—Alloys based on tin
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C13/00—Alloys based on tin
- C22C13/02—Alloys based on tin with antimony or bismuth as the next major constituent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/36—Electric or electronic devices
- B23K2101/42—Printed circuits
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- Organic Chemistry (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
The invention relates to a lead-free solder alloy, an electronic circuit board, and an electronic control device. Providing: a lead-free solder alloy which can suppress the progress of cracks in a solder joint and the electrode peeling phenomenon of an electronic component due to the solder joint in a severe environment such as a large cold-warm temperature difference and load vibration, and can suppress the progress of cracks in the vicinity of the interface between the electronic component and the solder joint even when the solder joint is performed using an electronic component not plated with Ni/Pd/Au, and an electronic circuit board and an electronic control device having the solder joint. The lead-free solder alloy is characterized by containing: 1 to 4 wt% of Ag, 0.5 to 1 wt% of Cu, 1 to 5 wt% of Sb, and at least one of Ni and Co in a total amount of 0.05 to 0.25 wt%, and contains Sn as a main component.
Description
Technical Field
The present invention relates to a lead-free solder alloy that can suppress the progress of cracking at a solder joint and the electrode peeling phenomenon of an electronic component due to the solder joint even in an environment subjected to a severe thermal shock cycle and a vibration load, and an electronic circuit board and an electronic control device each having the solder joint.
Background
Conventionally, when an electronic component is bonded to an electronic circuit formed on a substrate such as a printed circuit board or a silicone wafer, a solder bonding method using a solder paste composition has been employed. Solder alloys containing lead are generally used in the solder paste composition. However, in view of environmental load, the use of lead is limited by RoHS directive and the like, and thus, in recent years, a soldering method using a so-called lead-free solder alloy containing no lead has been becoming common.
As the lead-free solder alloy, for example, Sn-Cu based, Sn-Ag-Cu based, Sn-Bi based, Sn-Zn based solder alloys and the like are known. Among them, Sn-3Ag-0.5Cu solder alloys are often used for consumer electronic devices used in televisions, cellular phones, and the like, and for in-vehicle electronic devices mounted on automobiles.
The lead-free solder alloy is slightly inferior to the lead-containing solder alloy in solderability, but the problem of solderability is overcome by the improvement of the flux and the soldering apparatus. Therefore, even in the case of an on-vehicle electronic circuit board, for example, when the board is placed in a relatively stable environment despite a temperature difference between cold and warm temperatures as in the interior of an automobile, a solder joint formed using an Sn-3Ag-0.5Cu solder alloy does not have a significant problem.
However, in recent years, for example, as in an electronic circuit board used in an electronic control device, the arrangement of the electronic circuit board in a severe environment such as an engine room, an engine direct load, and electromechanical integration with a motor has been studied and put into practical use, because of a particularly large temperature difference between cold and warm temperatures (for example, temperature difference between-30 ℃ and 110 ℃, -40 ℃ and 125 ℃, -40 ℃ and 150 ℃). In such an environment where the temperature difference between cold and warm temperatures is very large, a large stress is generated in the solder joint portion due to the difference in the linear expansion coefficient between the mounted electronic component and the substrate. This stress, which is repeatedly generated in the solder joint together with the cold-heat cycle, often causes plastic deformation of the solder joint. Therefore, cracks are very likely to occur in the solder joint portion that has been repeatedly plastically deformed, and since strain concentrates in the solder joint portion near the tip where cracks have occurred, cracks tend to progress transversely to the deep portion of the solder joint portion. In addition, cracks and their progression are more likely to occur in an environment where vibration is applied to the electronic circuit board in addition to a large temperature difference between cold and warm temperatures. Such a remarkably progressing crack cuts off electrical connection between the electronic component and the electronic circuit formed on the substrate.
In the course of increasing number of electronic control devices and electronic circuit boards for mounting on vehicles which are exposed to the above severe environments, it is expected that the demand for solder paste compositions using Sn — Ag — Cu-based solder alloys which can exhibit a sufficient crack progression suppression effect will be increasing in the future.
In addition, Ni/Pd/Au-plated components have been used in many cases for lead portions of electronic components such as QFP (Quad flat package) and SOP (Small out line package) mounted on a vehicle-mounted electronic circuit board. However, with the recent reduction in cost of electronic components and the miniaturization of substrates, research and practical use of electronic components having lead portions replaced with Sn plating layers and electronic components having lower electrodes have been underway.
In the case of soldering, mutual diffusion of Sn plating layer, Sn contained in the soldered portion, and Cu contained in the lead portion and the lower surface electrode is likely to occur in the Sn-plated electronic component. The interdiffusion causes an intermetallic compound Cu to be present in the vicinity of the interface between the lead portion and the lower electrode and the solder joint3The Sn layer grows largely in a convex-concave shape. The aforementioned Cu3The Sn layer is originally hard and brittle, and Cu is grown in a convex-concave shape3The Sn layer becomes more brittle. Therefore, in particular, under the severe environment, cracks are more likely to occur in the vicinity of the interface than in the solder joint portion, and the generated cracks rapidly progress from this crack as a starting point, so that an electrical short circuit is more likely to occur.
Therefore, in the future, when an electronic component not plated with Ni/Pd/Au is used in such a severe environment as described above, it is expected that the demand for a lead-free solder alloy that can exhibit the effect of suppressing the progress of cracks in the vicinity of the interface will increase.
Several methods have been disclosed for increasing the strength of lead-free solder alloys by adding elements such as Ag and Bi to solder alloys using Sn as a base material (patent documents 1 to 7). However, only with the high strength of lead-free solder alloys, it is difficult to suppress the progress of cracks once generated in the solder joints.
In addition, the addition of Bi has a disadvantage that the high-strength lead-free solder alloy has poor stretchability. The applicant has confirmed that a solder joint formed using a conventional lead-free solder alloy containing Bi is exposed to an environment having a large temperature difference between cold and warm temperatures, and found that the solder joint has a certain crack-propagation-suppressing effect, but the solder joint peels off an electrode of an electronic component to cause a short circuit. Such a phenomenon is clearly observed when chip components of 3.2mm × 1.6mm size are used.
In a cooling process in a solder joining step by reflow soldering, a solder alloy is usually solidified from the electronic circuit side of a substrate to the electrode side of an electronic component, thereby forming a solder joint. Therefore, the residual stress is likely to be accumulated in the upper portion of the solder joint. Here, the lead-free solder alloy with reduced stretchability due to the addition of Bi is difficult to relax the residual stress, and cracks are likely to occur up to the deep portion in the vicinity of the electronic component electrode at the solder joint portion particularly in an environment with a large temperature difference between cold and warm temperatures. As a result, it is presumed that stress is concentrated on the electrode of the electronic component near the crack, and the solder joint peels off the electrode on the electronic component side.
This phenomenon is not observed in Sn-3Ag-0.5Cu solder alloys having good stretchability, and therefore, the danger caused by the addition of Bi to lead-free solder alloys can be captured. That is, it is considered that it is difficult to suppress the electrode peeling phenomenon of the electronic component only by the high strength of the lead-free solder alloy.
In the case of soldering an electronic component without plating Ni/Pd/Au, Cu, which is an intermetallic compound, is present in the vicinity of the interface between the lead portion and the lower surface electrode and the solder joint portion3Since the Sn layer grows largely in a convex-concave shape, it is difficult to suppress the progress of cracks in the vicinity of the interface.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 5-228685
Patent document 2: japanese laid-open patent publication No. 9-326554
Patent document 3: japanese patent laid-open No. 2000-190090
Patent document 4: japanese patent laid-open No. 2000-349433
Patent document 5: japanese patent laid-open No. 2008-28413
Patent document 6: international publication pamphlet No. WO2009/011341
Patent document 7: japanese laid-open patent publication No. 2012-81521
Disclosure of Invention
Problems to be solved by the invention
The present invention can solve the above problems, and an object thereof is to provide: a lead-free solder alloy, an electronic circuit board and an electronic control device having the solder joint, wherein the progress of cracks in the solder joint and the peeling-off of electrodes of an electronic component by the solder joint are suppressed at the same time even in a severe environment such as a large cold-warm temperature difference and load vibration, and the progress of cracks in the vicinity of the interface between the electronic component and the solder joint is suppressed even when the solder joint is performed using an electronic component not plated with Ni/Pd/Au.
Means for solving the problems
(1) The lead-free solder alloy of the present invention is characterized by containing: 1 to 4 wt% of Ag, 0.5 to 1 wt% of Cu, 1 to 5 wt% of Sb, and at least one of Ni and Co in a total amount of 0.05 to 0.25 wt%, and contains Sn as a main component.
(2) In the configuration described In (1) above, the lead-free solder alloy of the present invention is characterized by further containing 6 wt% or less of In.
(3) In the above-described configuration (1) or (2), the lead-free solder alloy of the present invention is characterized by further containing 3% by weight or less of Bi.
(4) In the configuration of any one of (1) to (3), the lead-free solder alloy of the present invention is characterized by further containing 8 wt% or less of Zn.
(5) In the configuration described in any one of (1) to (4), the lead-free solder alloy of the present invention is characterized by further containing at least 1 kind of Fe, Mn, Cr, and Mo in a total amount of 0.001 wt% or more and 0.05 wt% or less.
(6) In the configuration described in any one of (1) to (5) above, the lead-free solder alloy of the present invention is characterized by further containing P, Ga and at least 1 of Ge in a total amount of 0.001 wt% to 0.05 wt%.
(7) An electronic circuit board of the present invention is characterized by having a solder joint portion formed using the lead-free solder alloy according to any one of (1) to (6) above.
(8) An electronic control device of the present invention is characterized by comprising the electronic circuit board according to (7) above.
ADVANTAGEOUS EFFECTS OF INVENTION
The lead-free solder alloy, the electronic circuit board having the solder joint, and the electronic control device of the present invention can simultaneously suppress the progress of cracks in the solder joint and the electrode peeling phenomenon of the electronic component due to the solder joint even in a severe environment such as a large cold-warm temperature difference and load vibration, and can suppress the progress of cracks in the vicinity of the interface between the electronic component and the solder joint even when the solder joint is performed using an electronic component not plated with Ni/Pd/Au.
Drawings
Fig. 1 is a partial sectional view showing a part of an electronic circuit substrate according to an embodiment of the present invention.
Fig. 2 is a photograph showing a cross section of a chip resistor (chipmaker) in which an electrode peeling phenomenon of an electronic component occurs in a comparative example of the present invention.
Description of the reference numerals
1 substrate
2 insulating layer
3 electrode part
4 electronic component
5 external electrode
6 solder joint
7 flux residue
8 end part
10 solder joint body
100 electronic circuit board
Detailed Description
Hereinafter, one embodiment of the lead-free solder alloy, the electronic circuit board, and the electronic control device according to the present invention will be described in detail. Needless to say, the present invention is not limited to the following embodiments.
(1) Leadless soft solder alloy
The lead-free solder alloy of the present embodiment contains: 1 to 4 wt% of Ag, 0.5 to 1 wt% of Cu, 1 to 5 wt% of Sb, and at least one of Ni and Co in a total amount of 0.05 to 0.25 wt%, and contains Sn as a main component.
The lead-free solder alloy of the present embodiment may contain 1 wt% to 4 wt% of Ag. Adding Ag to the solution3The Sn compound precipitates in Sn grain boundaries of the lead-free solder alloy, and can impart mechanical strength.
However, when the content of Ag is less than 1 wt%, Ag3The precipitation of Sn compounds is not preferable because the mechanical strength and thermal shock resistance of the lead-free solder alloy are reduced. When the content of Ag exceeds 4 wt%, the stretchability of the lead-free solder alloy is inhibited, and the solder joint formed using the alloy may cause an electrode peeling phenomenon in the electronic component, which is not preferable.
When the content of Ag is 2 wt% or more and 3.8 wt% or less, the balance between the strength and the stretchability of the lead-free solder alloy can be further improved.
The lead-free solder alloy of the present embodiment may contain 0.5 wt% or more and 1 wt% or less of Cu. By adding Cu in this range, Cu corrosion prevention effect on Cu pads of electronic circuits can be exhibited, and Cu can be made to be present6Sn5Since the compound precipitates in the Sn grain boundary, the thermal shock resistance of the lead-free solder alloy can be improved. In this embodiment, Cu is particularly preferableThe content is 0.5 wt% or 0.9 wt% to 1 wt%.
When the Cu content is less than 0.5% by weight, a sufficient Cu corrosion preventing effect cannot be obtained, and when the Cu content exceeds 1% by weight, Cu is contained6Sn5The compound is not preferable because it is precipitated intensively in the vicinity of the bonding interface, the bonding reliability is lowered, and the stretchability of the lead-free solder alloy is inhibited.
In particular, when the content of Cu is 0.5 wt%, the Cu corrosion prevention effect on the Cu land can be exhibited, the viscosity of the lead-free solder alloy at the time of melting can be kept in a good state, the generation of voids at the time of reflow soldering can be suppressed, and the thermal shock resistance of the solder joint formed can be improved.
Further, when the content of Cu is 0.9 to 1 wt%, the Cu corrosion prevention effect on the Cu pad can be sufficiently exhibited, and diffusion of Cu from the Cu pad to the molten lead-free solder alloy can be prevented, whereby Cu on the electronic component side can be prevented6Sn5The coarsening of the compound is suppressed, and the thermal shock resistance of the solder joint can be improved. Further, fine Cu6Sn5By dispersing into the Sn grain boundary of the molten lead-free solder alloy, the change in the crystal orientation of Sn is suppressed, and the deformation of the solder joint shape (fillet shape) can be suppressed.
When Cu is contained in the lead-free solder alloy, if the amount thereof is large, Cu is contained as described above6Sn5The compound is likely to precipitate in the vicinity of the bonding interface, and there is a concern that the bonding reliability and the stretchability of the lead-free solder alloy are impaired. However, if the lead-free alloy of the present embodiment is configured, the Cu content can be suppressed even if the Cu content is 0.9 to 1 wt%6Sn5The coarsening of the compound and the good stretchability thereof are maintained, and the decrease in bonding reliability can be suppressed.
The lead-free solder alloy of the present embodiment may contain Sb in an amount of 1 to 5 wt%. By adding Sb in this range, the effect of suppressing the progress of cracks in the solder joint can be improved without impairing the stretchability of the Sn-Ag-Cu solder alloy. In particular, when the content of Sb is 2% by weight or more and 4% by weight or less, the crack growth suppression effect can be further improved.
Here, in order to withstand external stress in a severe environment where a temperature difference between cold and warm temperatures is large after long-term exposure, it is considered effective to improve toughness (the size of an area surrounded by a stress-strain curve) of the lead-free solder alloy, to improve stretchability, and to add an element that is solid-dissolved in the Sn matrix to perform solid-solution strengthening. Sb is an optimum element for ensuring sufficient toughness and elongation and for performing solid-solution strengthening of the lead-free solder alloy.
That is, in a lead-free solder alloy substantially containing Sn as a base material, Sb is added in the above-described range, whereby a part of the lattice of Sn is replaced with Sb, and distortion occurs in the lattice. Therefore, in the solder joint formed using such a lead-free solder alloy, energy required for transfer in the crystal is increased by Sb substitution in a part of the Sn lattice, and the microstructure is strengthened. Further, fine SnSb, ε -Ag3Since the (Sn, Sb) compound precipitates in Sn grain boundaries, the progress of cracks generated in the solder joints can be suppressed by preventing sliding deformation of Sn grain boundaries.
Further, it was confirmed that compared with the Sn-3Ag-0.5Cu solder alloy, the structure of the solder joint formed by using the lead-free solder alloy containing Sb in the above-mentioned range is maintained in a fine state even after the structure is exposed to a severe environment having a large temperature difference between cold and warm temperatures for a long time, and cracks hardly progress. This is considered to be due to SnSb and ε -Ag precipitating in Sn grain boundaries3The (Sn, Sb) compound is finely dispersed in the solder joint even after being exposed to a severe environment having a large temperature difference between cold and warm temperatures for a long time, and therefore coarsening of Sn crystals can be suppressed. That is, it is considered that the solder joint using the lead-free solder alloy to which Sb is added in the above-mentioned range causes solid solution of Sb in the Sn matrix in a high temperature state and causes SnSb and ε -Ag in a low temperature state3Since the (Sn, Sb) compound is precipitated, the step of solid solution strengthening is repeated at a high temperature when the film is exposed to a severe environment having a large temperature difference between cold and warm for a long timeBy repeating the precipitation strengthening step at a low temperature, excellent thermal shock resistance can be ensured.
Further, the lead-free solder alloy containing Sb in the above-mentioned range can improve the strength of the Sn-3Ag-0.5Cu solder alloy without lowering the stretchability thereof, and therefore, can secure sufficient toughness against external stress and can also relax residual stress, and therefore, can suppress cracking at the solder joint and electrode peeling of the electronic component even when exposed to a severe environment having a large temperature difference between cold and warm temperatures for a long time.
However, if the content of Sb exceeds 5 wt%, the melting temperature of the lead-free solder alloy increases, and Sb does not dissolve in a solid solution at high temperatures. Therefore, when the film is exposed to a severe environment with a large temperature difference between cold and warm for a long time, only SnSb and epsilon-Ag are used3Since the precipitation of the (Sn, Sb) compound is intensified, these intermetallic compounds coarsen with the passage of time, and the effect of suppressing the sliding deformation of the Sn grain boundary is lost. In addition, in the above case, the heat-resistant temperature of the electronic component is also a problem with an increase in the melting temperature of the lead-free solder alloy, which is not preferable.
The lead-free solder alloy of the present embodiment may contain at least one of Ni and Co in a total amount of 0.05 wt% to 0.25 wt%. When an electronic component not plated with Ni/Pd/Au is solder-bonded using the lead-free solder of the present embodiment by adding at least one of Ni and Co within this range, Ni and/or Co moves to the vicinity of the interface between the electronic component and the solder-bonded portion at the time of solder bonding to form fine (Cu, Ni)6Sn5And/or (Cu, Co)6Sn5Therefore, Cu in the vicinity of the interface thereof3The growth of the Sn layer is suppressed. This can improve the crack-propagation-suppressing effect in the vicinity of the interface.
However, if the content of at least one of Ni and Co is less than 0.05 wt%, the amount of Ni and/or Co in the vicinity of the interface is reduced, and the effect of modifying the intermetallic compound is insufficient, so that it is difficult to obtain a sufficient crack-inhibiting effect. When the content of at least one of Ni and Co exceeds 0.25 wt%, the lead-free solder alloy is easily oxidized and wettability thereof is inhibited, which is not preferable.
The content of at least one of Ni and Co is preferably 0.05 wt% or more and 0.25 wt% or less, and more preferably 0.05 wt% or more and 0.15 wt% or less.
In addition, if the lead-free solder alloy of the present embodiment contains at least one of Ni and Co in an amount of 0.05 wt% or more, these components form fine (Cu, Ni) at the interface between the electronic component and the solder joint6Sn5Or (Cu, Co)6Sn5(both of them are included), therefore, the crack progression suppression effect can be improved.
When both Ni and Co are contained in the lead-free solder alloy according to the present embodiment, the mass ratio of the content of Ni to the content of Co (Ni/Co) is preferably 0.25 to 4.
Further, when any one of Ni and Co is contained in the lead-free solder alloy according to the present embodiment, the content thereof is preferably 0.05 to 0.25 wt%, and more preferably 0.05 to 0.15 wt%.
The lead-free solder alloy according to the present embodiment may contain 6 wt% or less of In. By adding In this range, the melting temperature of the lead-free solder alloy increased by the addition of Sb can be lowered, and the crack growth suppression effect can be improved. That is, In is also solid-dissolved In the Sn matrix similarly to Sb, and therefore, not only can the lead-free solder alloy be further strengthened, but also the effect of suppressing the sliding deformation at Sn grain boundaries is exerted by forming AgSnIn and InSb compounds and causing precipitation at the Sn grain boundaries.
When the In content In the solder alloy of the present invention exceeds 6% by weight, the elongation of the lead-free solder alloy can be inhibited, and γ -InSn can be formed during long-term exposure to a severe environment having a large temperature difference between cold and warm temperatures4Lead-free solder alloys are not preferred because they deform themselves.
The In content is more preferably 4% by weight or less, and particularly preferably 1% by weight to 2% by weight.
Further, the lead-free solder alloy of the present embodiment may contain 3 wt% or less of Bi. In the configuration of the lead-free solder alloy according to the present embodiment, when Bi is added within this range, the tensile properties of the lead-free solder alloy are not affected, the strength thereof can be improved, and the melting temperature increased by the addition of Sb can be reduced. That is, since Bi is also solid-solved in the Sn matrix as in Sb, the lead-free solder alloy can be further strengthened. However, when the content of Bi exceeds 3 wt%, the stretchability of the lead-free solder alloy is lowered, and when the lead-free solder alloy is exposed to a severe environment having a large temperature difference between cold and warm temperatures for a long time, the solder joint portion formed of the lead-free solder alloy is liable to cause an electrode peeling phenomenon in the electronic component, which is not preferable.
The lead-free solder alloy of the present embodiment may contain 8 wt% or less of Zn. By adding Zn in this range, the creep resistance and crack growth suppression effect of the solder joint formed using the lead-free solder alloy can be improved, and the melting temperature increased by the addition of Sb can be reduced. That is, by adding Zn, a solder joint/Cu can be formed5Zn8/Cu6Sn5The interface structure of Cu suppresses the growth of intermetallic compounds in the solder joint when exposed to a severe environment with a large temperature difference between cold and warm temperatures for a long time. However, when the Zn content exceeds 8 wt%, the lead-free solder alloy is easily oxidized to inhibit the wettability, which is not preferable.
The more preferable content of Zn is 5 wt% or less, and the more preferable content is 3 wt% or less.
The lead-free solder alloy according to the present embodiment may contain 0.001 wt% to 0.05 wt% of at least 1 of Fe, Mn, Cr, and Mo. By adding at least 1 of Fe, Mn, Cr, and Mo within this range, the crack growth suppression effect of the lead-free solder alloy can be improved. However, when the content of these elements exceeds 0.05 wt%, the melting temperature of the lead-free solder alloy increases, and voids are likely to be generated in the solder joint, which is not preferable.
Further, the lead-free solder alloy of the present embodiment may contain P, Ga and at least 1 of Ge in an amount of 0.001 wt% to 0.05 wt%. By adding P, Ga and at least 1 of Ge in this range, oxidation of the lead-free solder alloy can be prevented. However, when the content of these elements exceeds 0.05 wt%, the melting temperature of the lead-free solder alloy increases, and voids are likely to be generated in the solder joint, which is not preferable.
The lead-free solder alloy according to the present embodiment may contain other components (elements) such as Cd, Tl, Se, Au, Ti, Si, Al, and Mg, within a range that does not inhibit the effects thereof. Needless to say, the lead-free solder alloy of the present embodiment may contain inevitable impurities.
In addition, the lead-free solder alloy of the present embodiment preferably contains Sn as a main component. The amount of Sn blended is preferably 72.65 to 97.45 wt%.
(2) Solder paste composition
The solder paste composition used for the electronic circuit board and the electronic control device of the present embodiment is produced by, for example, kneading the lead-free solder alloy in powder form and the flux to form a paste.
As such a flux, for example, a flux containing a synthetic resin, a thixotropic agent, an active agent, and a solvent can be used.
Examples of the synthetic resin include: acrylic resins obtained by polymerizing at least 1 monomer selected from acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic anhydride, esters of maleic acid, esters of maleic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and vinyl chloride-vinyl acetate, derivative compounds obtained by dehydrating and condensing a rosin-based resin having a carboxyl group and a dimer acid derivative flexible alcohol compound, epoxy resins, phenol resins, and rosin-based resins. They may be used alone or in combination of plural kinds.
Among the above acrylic resins, the following are particularly preferably used: an acrylic resin obtained by polymerizing methacrylic acid with a monomer having a saturated alkyl group having 2 carbon chains of 2 to 20 carbon atoms, the monomer being linear.
The rosin resin having a carboxyl group used in a derivative compound (hereinafter referred to as "rosin derivative compound") obtained by dehydrating and condensing the rosin resin having a carboxyl group and a dimer acid derivative flexible alcohol compound includes, for example: tall oil rosin, gum rosin, wood rosin and other rosins; rosin derivatives such as hydrogenated rosin, polymerized rosin, disproportionated rosin, acrylic acid-modified rosin, and maleic acid-modified rosin, and other rosin derivatives may be used as long as they are rosins having a carboxyl group. In addition, they may be used alone or in combination of plural kinds.
Next, examples of the dimer acid derivative-flexible alcohol compound include: compounds derived from dimer acids and having an alcohol group at the terminal thereof, such as diol, polyester polyol, and polyester diol, for example, can be used as follows: PRIPOL2033, PRIPOLAT 3197, PRIPOLAT 1838 (manufactured by Croda Japan KK., supra), and the like.
The rosin derivative compound is obtained by dehydrating and condensing the rosin resin having a carboxyl group and the dimer acid derivative-flexible alcohol compound. As the dehydration condensation method, a commonly used method can be used. The preferable weight ratio of the rosin-based resin having a carboxyl group to the dimer acid derivative flexible alcohol compound in the dehydration condensation is 25:75 to 75:25, respectively.
The acid value of the synthetic resin is preferably 10mgKOH/g to 150mgKOH/g, and the amount of the synthetic resin is preferably 10 wt% to 90 wt% based on the total amount of the flux.
Examples of the thixotropic agent include: hydrogenated castor oil, fatty acid amides, hydroxy fatty acids. They may be used alone or in combination of plural kinds. The amount of the thixotropic agent is preferably 3 wt% or more and 15 wt% or less based on the total amount of the flux.
The activator may be, for example, an amine salt (inorganic acid salt, organic acid salt) such as a hydrogen halide salt of an organic amine, an organic acid salt, or an organic amine salt. More specifically, there may be mentioned: diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salt, acid salt, succinic acid, adipic acid, sebacic acid, and the like. They may be used alone or in combination of plural kinds. The amount of the active agent is preferably 5 wt% or more and 15 wt% or less with respect to the total amount of the flux.
As the aforementioned solvent, for example, there can be used: isopropanol, ethanol, acetone, toluene, xylene, ethyl acetate, ethyl cellosolve, butyl cellosolve, glycol ether, and the like. They may be used alone or in combination of plural kinds. The amount of the solvent is preferably 20 wt% or more and 40 wt% or less with respect to the total amount of the flux.
In order to suppress oxidation of the lead-free solder alloy, an antioxidant agent may be added to the flux. Examples of the antioxidant include: hindered phenol antioxidants, bisphenol antioxidants, polymer antioxidants, and the like. Among them, a hindered phenol-based oxidizing agent is particularly preferably used. They may be used alone or in combination of plural kinds. The amount of the antioxidant is not particularly limited, but is preferably 0.5 wt% or more and 5 wt% or less with respect to the total amount of the flux in general.
Other additives such as resins, halogens, matting agents and defoaming agents may be added to the above flux.
The amount of the additive is preferably 10 wt% or less based on the total amount of the flux. Further, a more preferable blending amount of these is 5 wt% or less with respect to the total amount of the flux.
The flux residue formed from the flux can be preferably maintained at 0.2N/mm in adhesive strength after 2000 cycles of a cold-heat impact test in which 1 cycle of-40 ℃/30 minutes to 125 ℃/30 minutes is applied thereto2The above. By using a flux capable of forming such a flux residue, the flux residue firmly adheres the substrate, the solder joint portion, and the electronic component to each other and is cured and contracted by itself, and therefore, even in cold or warm environmentsEven in an environment with a large temperature difference, cracks are generated in the solder joint portion, and strain concentrated near the tips of the generated cracks is dispersed, so that the opening of the crack surface can be prevented, and the progress of the cracks can be suppressed.
In the present specification, the adhesive strength of the flux residue is measured by the following measurement method.
A chip component is surface-mounted on a substrate by using a flux or a solder paste composition using the flux, and a flux residue is formed on the substrate. The flux residue is present in a space surrounded by the substrate, the chip component, and the solder joint portion, and is formed so as to adhere to them.
Thereafter, the substrate was subjected to a cold thermal shock test of 1 cycle at-40 ℃/30 minutes to 125 ℃/30 minutes using a cold thermal shock test apparatus or the like for 2000 cycles.
Then, the adhesion of the flux residue on the substrate after the cold-thermal shock test was measured by Autograph or the like. The measurement conditions were as specified in JIS C60068-2-21. The jig used for the measurement is a shearing jig having a flat end face and a width equal to or larger than the size of the member. In the measurement, the shear jig is fixed to the side surface of the chip component after the thermal shock test, a parallel force is applied to the substrate at a predetermined shear rate to obtain a maximum test force, and the maximum test force is divided by the area of the chip component to calculate the adhesive force of the flux residue. At this time, the shearing height was 1/4 or less, and the shearing speed was 5 mm/min.
The mixing ratio of the lead-free solder alloy to the flux is preferably 65:35 to 95:5 in terms of the ratio of the solder alloy to the flux. The compounding ratio is more preferably 85:15 to 93:7, and the compounding ratio is particularly preferably 89:11 to 92: 8.
(3) Electronic circuit board
The structure of the electronic circuit board according to the present embodiment will be described with reference to fig. 1. The electronic circuit board 100 of the present embodiment includes: substrate 1, insulating layer 2, electrode portion 3, electronic component 4, and solder joint 10. The solder joint body 10 includes a solder joint portion 6 and a flux residue 7, and the electronic component 4 includes an external electrode 5 and an end portion 8.
The substrate 1 is not limited to this as long as it is a substrate used for mounting and mounting electronic components, such as a printed circuit board, a silicone wafer, or a ceramic package substrate, and can be used as the substrate 1.
The electrode portion 3 is electrically connected to the external electrode 5 of the electronic component 4 via the solder joint portion 6. The flux residue 7 is formed so as to fill a space surrounded by the insulating layer 2, the solder joint 6, and the electronic component 4 and adhere to them. Further, the separate flux residue 7 is also formed so as to cover the insulating layer 2, the solder joint portion 6, and the end portion 8 of the electronic component 4.
Since the solder joint portion 6 of the electronic circuit board 100 of the present embodiment having such a configuration is an alloy composition that exhibits the effect of suppressing the progress of cracks and the electrode peeling phenomenon, even when cracks are generated in the solder joint portion 6, the progress of the cracks can be suppressed and the electrode peeling phenomenon of the electronic component 4 can be suppressed.
Further, the flux residue 7 of the electronic circuit board 100 of the present embodiment more firmly adheres the insulating layer 2, the solder joint portion 6, and the electronic component 4, and by such a configuration, the effect of suppressing the above-described crack progression and the electrode peeling phenomenon can be further improved.
Such an electronic circuit board 100 can be manufactured, for example, as follows.
First, the solder paste composition is printed on the substrate 1 including the insulating layer 2 and the electrode portion 3 formed to have a predetermined pattern in accordance with the pattern.
Next, the electronic component 4 is mounted on the printed board 1, and reflow soldering is performed at a temperature of 220 to 260 ℃. By this reflow soldering, a solder joint 10 having a solder joint portion 6 and a flux residue 7 is formed on the substrate 1, and an electronic circuit board 100 in which the substrate 1 and the electronic component 4 are electrically joined is manufactured.
By assembling such an electronic circuit board, the electronic control device of the present embodiment can be manufactured.
Examples
The present invention will be described in detail below with reference to examples and comparative examples. The present invention is not limited to these examples.
Preparation of soldering flux
The following components were kneaded to obtain fluxes of examples and comparative examples.
51% by weight of hydrogenated acid-modified rosin (trade name: KE-604, manufactured by Mitsukawa chemical industries, Ltd.)
Hardened castor oil 6% by weight
Icosanedioic acid 5% by weight
Malonic acid 1% by weight
Diphenylguanidine hydrobromide 2% by weight
Hindered phenol antioxidant (product name: IRGANOX 245, manufactured by BASF Japan Ltd.) 1% by weight
Diethylene glycol Monohexyl ether 34% by weight
Preparation of solder paste composition
Solder paste compositions of examples 1 to 80 (tables 1 to 3) and comparative examples 1 to 34 (tables 4 to 5) were prepared by mixing 11.0 wt% of the flux with 89.0 wt% of the powder (powder particle size 20 μm to 36 μm) of each lead-free solder alloy described in tables 1 to 5.
[ Table 1]
| Sn | Ag | Cu | Sb | Ni | Co | In | Bi | Zn | Others | |
| Example 1 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | - | - | - |
| Example 2 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | - | - | - |
| Example 3 | Balance of | 3.0 | 0.9 | 1.0 | 0.15 | - | - | - | - | - |
| Example 4 | Balance of | 3.0 | 0.9 | 5.0 | 0.15 | - | - | - | - | - |
| Example 5 | Balance of | 3.0 | 1.0 | 1.0 | 0.15 | - | - | - | - | - |
| Example 6 | Balance of | 3.0 | 1.0 | 5.0 | 0.15 | - | - | - | - | - |
| Example 7 | Balance of | 1.0 | 0.5 | 1.0 | 0.15 | - | - | - | - | - |
| Example 8 | Balance of | 1.0 | 0.5 | 5.0 | 0.15 | - | - | - | - | - |
| Example 9 | Balance of | 2.0 | 0.5 | 1.0 | 0.15 | - | - | - | - | - |
| Example 10 | Balance of | 2.0 | 0.5 | 5.0 | 0.15 | - | - | - | - | - |
| Example 11 | Balance of | 3.8 | 0.5 | 1.0 | 0.15 | - | - | - | - | - |
| Example 12 | Balance of | 3.8 | 0.5 | 5.0 | 0.15 | - | - | - | - | - |
| Example 13 | Balance of | 4.0 | 0.5 | 1.0 | 0.15 | - | - | - | - | - |
| Example 14 | Balance of | 4.0 | 0.5 | 5.0 | 0.15 | - | - | - | - | - |
| Example 15 | Balance of | 3.0 | 0.5 | 5.0 | 0.05 | - | - | - | - | - |
| Example 16 | Balance of | 3.0 | 0.5 | 5.0 | 0.25 | - | - | - | - | - |
| Example 17 | Balance of | 3.0 | 0.5 | 5.0 | - | 0.05 | - | - | - | - |
| Example 18 | Balance of | 3.0 | 0.5 | 5.0 | - | 0.15 | - | - | - | - |
| Example 19 | Balance of | 3.0 | 0.5 | 5.0 | - | 0.25 | - | - | - | - |
| Example 20 | Balance of | 3.0 | 0.5 | 5.0 | 0.05 | 0.20 | - | - | - | - |
| Example 21 | Balance of | 3.0 | 0.5 | 5.0 | 0.10 | 0.15 | - | - | - | - |
| Example 22 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | 0.10 | - | - | - | - |
| Example 23 | Balance of | 3.0 | 0.5 | 5.0 | 0.20 | 0.05 | - | - | - | - |
| Example 24 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 0.5 | - | - | - |
| Example 25 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 0.5 | - | - | - |
| Example 26 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 4.0 | - | - | - |
| Example 27 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 4.0 | - | - | - |
| Example 28 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 6.0 | - | - | - |
| Example 29 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.0 | - | - | - |
| Example 30 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | 0.5 | - | - |
[ Table 2]
| Sn | Ag | Cu | Sb | Ni | Co | In | Bi | Zn | Others | |
| Example 31 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | 0.5 | - | - |
| Example 32 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | 1.0 | - | - |
| Example 33 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | 1.0 | - | - |
| Example 34 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | 2.0 | - | - |
| Example 35 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | 2.0 | - | - |
| Example 36 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | 3.0 | - | - |
| Example 37 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | 3.0 | - | - |
| Example 38 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 0.5 | 0.5 | - | - |
| Example 39 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 4.0 | 0.5 | - | - |
| Example 40 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 6.0 | 0.5 | - | - |
| EXAMPLE 41 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 0.5 | 0.5 | - | - |
| Example 42 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | - |
| Example 43 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 6.0 | 0.5 | - | - |
| Example 44 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 0.5 | 0.5 | - | - |
| Example 45 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 4.0 | 0.5 | - | - |
| Example 46 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.0 | 0.5 | - | - |
| Example 47 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 0.5 | 3.0 | - | - |
| Example 48 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 4.0 | 3.0 | - | - |
| Example 49 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 6.0 | 3.0 | - | - |
| Example 50 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 0.5 | 3.0 | - | - |
| Example 51 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 3.0 | - | - |
| Example 52 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 6.0 | 3.0 | - | - |
| Example 53 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 0.5 | 3.0 | - | - |
| Example 54 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 4.0 | 3.0 | - | - |
| Example 55 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.0 | 3.0 | - | - |
| Example 56 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | - | 0.5 | - |
| Example 57 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | - | 0.5 | - |
| Example 58 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | - | 3 | - |
| Example 59 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | - | 3 | - |
| Example 60 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | - | 5 | - |
[ Table 3]
| Sn | Ag | Cu | Sb | Ni | Co | In | Bi | Zn | Others | |
| Example 61 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | - | 5 | - |
| Example 62 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | - | 8 | - |
| Example 63 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | - | 8 | - |
| Example 64 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 0.5 | 0.5 | 0.5 | - |
| Example 65 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 0.5 | 0.5 | 8 | - |
| Example 66 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.0 | 3.0 | 0.5 | - |
| Example 67 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.0 | 3.0 | 8 | - |
| Example 68 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.05Fe |
| Example 69 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.05Mn |
| Example 70 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.05Cr |
| Example 71 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.05Mo |
| Example 72 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.05P |
| Example 73 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.05Ga |
| Example 74 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.05Ge |
| Example 75 | Balance of | 3.0 | 1.0 | 3.0 | 0.05 | 0.05 | - | 3.0 | - | - |
| Example 76 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | - | 3.0 | - | - |
| Example 77 | Balance of | 3.8 | 0.5 | 3.0 | 0.15 | - | - | 3.0 | - | - |
| Example 78 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 1.0 | 3.0 | - | - |
| Example 79 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 2.0 | 3.0 | - | - |
| Example 80 | Balance of | 3.0 | 0.5 | 4.0 | 0.15 | - | - | - | - | - |
[ Table 4]
| Sn | Ag | Cu | Sb | Ni | Co | In | Bi | Zn | Others | |
| Comparative example 1 | Balance of | 3.0 | 0.5 | - | - | - | - | - | - | - |
| Comparative example 2 | Balance of | 3.0 | 0.5 | 0.5 | 0.15 | - | - | - | - | - |
| Comparative example 3 | Balance of | 3.0 | 0.5 | 5.5 | 0.15 | - | - | - | - | - |
| Comparative example 4 | Balance of | 3.0 | 0.4 | 1.0 | 0.15 | - | - | - | - | - |
| Comparative example 5 | Balance of | 3.0 | 0.4 | 5.0 | 0.15 | - | - | - | - | - |
| Comparative example 6 | Balance of | 3.0 | 1.5 | 1.0 | 0.15 | - | - | - | - | - |
| Comparative example 7 | Balance of | 3.0 | 1.5 | 5.0 | 0.15 | - | - | - | - | - |
| Comparative example 8 | Balance of | 0.5 | 0.5 | 1.0 | 0.15 | - | - | - | - | - |
| Comparative example 9 | Balance of | 0.5 | 0.5 | 5.0 | 0.15 | - | - | - | - | - |
| ComparisonExample 10 | Balance of | 4.5 | 0.5 | 1.0 | 0.15 | - | - | - | - | - |
| Comparative example 11 | Balance of | 4.5 | 0.5 | 5.0 | 0.15 | - | - | - | - | - |
| Comparative example 12 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 6.5 | - | - | - |
| Comparative example 13 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.5 | - | - | - |
| Comparative example 14 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | 3.5 | - | - |
| Comparative example 15 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | 3.5 | - | - |
| Comparative example 16 | Balance of | 3.0 | 0.5 | 0.5 | 0.15 | - | 6.5 | 3.5 | - | - |
| Comparative example 17 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 6.5 | 3.5 | - | - |
| Comparative example 18 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 6.5 | 3.5 | - | - |
| Comparative example 19 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.5 | 3.5 | - | - |
| Comparative example 20 | Balance of | 3.0 | 0.5 | 5.5 | 0.15 | - | 6.5 | 3.5 | - | - |
| Comparative example 21 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | - | - | 8.5 | - |
| Comparative example 22 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | - | - | 8.5 | - |
| Comparative example 23 | Balance of | 3.0 | 0.5 | 0.5 | 0.15 | - | 6.5 | 3.5 | 8.5 | - |
| Comparative example 24 | Balance of | 3.0 | 0.5 | 1.0 | 0.15 | - | 6.5 | 3.5 | 8.5 | - |
| Comparative example 25 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 6.5 | 3.5 | 8.5 | - |
| Comparative example 26 | Balance of | 3.0 | 0.5 | 5.0 | 0.15 | - | 6.5 | 3.5 | 8.5 | - |
| Comparative example 27 | Balance of | 3.0 | 0.5 | 5.5 | 0.15 | - | 6.5 | 3.5 | 8.5 | - |
| Comparative example 28 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.1Fe |
| Comparative example 29 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.1Mn |
| Comparative example 30 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.1Cr |
[ Table 5]
| Sn | Ag | Cu | Sb | Ni | Co | In | Bi | Zn | Others | |
| Comparative example 31 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.1Mo |
| Comparative example 32 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.1P |
| Comparative example 33 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.1Ga |
| Comparative example 34 | Balance of | 3.0 | 0.5 | 3.0 | 0.15 | - | 4.0 | 0.5 | - | 0.1Ge |
(1) Solder cracking test
Preparing: chip components of 3.2mm by 1.6mm size; a glass epoxy substrate having a solder resist film having a pattern capable of mounting a chip component of the size and an electrode (1.6mm × 1.2mm) for connecting the chip component; and a metal mask having a thickness of 150 μm with the same pattern.
Using the metal mask, each solder paste composition was printed on the glass epoxy substrate, and the chip components were mounted thereon.
Thereafter, each of the glass epoxy boards was heated in a reflow furnace (product name: TNP-538EM, manufactured by TAMURA Corporation), and solder joints for electrically joining the glass epoxy board and the chip component were formed on the heated glass epoxy board, respectively, to mount the chip component. In the reflow conditions, the preheating was conducted at 170 to 190 ℃ for 110 seconds, the peak temperature was 245 ℃, the time of 200 ℃ or more was 65 seconds, the time of 220 ℃ or more was 45 seconds, the cooling rate from the peak temperature to 200 ℃ was 2 to 8 ℃/second, and the oxygen concentration was 1500. + -.500 ppm.
Next, each of the glass epoxy plates was exposed to an environment in which a cold-hot impact cycle was repeated for 1000 cycles, 1500 cycles, 2000 cycles, 2500 cycles, and 3000 cycles using a cold-hot impact testing apparatus (product name: ES-76LMS, Hitachi applications, inc.) set to conditions of-40 ℃ (30 minutes) to 125 ℃ (30 minutes), and then taken out to fabricate each test substrate.
Then, the target portion of each test substrate was cut out and sealed with an epoxy resin (product name: epocount (main agent and curing agent), manufactured by Refine Tec ltd. Further, the state in which the center cross section of the chip component mounted on each test substrate was observed was measured by using a wet grinder (product name: Tegrapol-25, manufactured by Marumoto struts K.K.), and whether or not the crack generated in the formed solder joint completely intersected the solder joint and broke was evaluated by the following criteria by using a scanning electron microscope (product name: TM-1000, manufactured by Hitachi High-technologies corporation). The results are shown in tables 6 to 10. The number of evaluation chips in each thermal shock cycle was 20.
◎ cracking did not occur completely across the solder joint up to 3000 cycles
○ cracks completely crossing the solder joint occurred between 2501 and 3000 cycles
△ cracks completely crossing the solder joint occurred between 2001 and 2500 cycles
X: crack generation at less than 2000 cycles completely transverse to solder joint
(2) Electrode peeling test
Each test substrate was prepared under the same conditions as in the solder cracking test except that each glass epoxy substrate was left in an environment in which the cold-hot impact cycle was repeated 1000 cycles, 1500 cycles, 2000 cycles, 2500 cycles, 3000 cycles, and 3500 cycles.
Next, the target portion of each test substrate was cut out and sealed with an epoxy resin (product name: epocount (main agent and curing agent), manufactured by Refine Tec ltd. Further, a wet grinder (product name: Tegrapol-25, manufactured by Marumoto struts K.K.) was used to observe the central cross section of the chip component mounted on each test substrate, and whether or not a phenomenon such that the solder joint portion peels off the electrode of the chip component as shown in FIG. 2 occurred was observed using a scanning electron microscope (product name: TM-1000, manufactured by Hitachi High-technologies corporation) and evaluated as follows. The number of evaluation chips in each thermal shock cycle was 20. The results are shown in tables 6 to 10.
◎ No chip part peeling off phenomenon occurred up to 3500 cycles
○ occurrence of electrode peeling phenomenon of chip component between 3001 and 3500 cycles
△ occurrence of electrode peeling phenomenon of chip component between 2001 and 3000 cycles
X: electrode peeling phenomenon of chip component generated in less than 2000 cycles
(3) Solder cracking test in Sn plating QFP
Preparing: a QFP part of 0.5mm pitch (lead number 176 pins, product name: R5F5630ADDFC, manufactured by Renesas Electronics Corporation) of 26mm by 1.6mmt size; a glass epoxy substrate having a solder resist having a pattern on which the QFP component can be mounted and electrodes (176 electrodes of 0.25mm × 1.3 mm) for connecting the QFP component; and a metal mask having a thickness of 150 μm with the same pattern.
Using the metal mask, each solder paste composition was printed on the glass epoxy substrate, and the QFP components were mounted thereon, respectively. Thereafter, each test substrate was produced by applying a thermal shock to the glass epoxy substrate under the same conditions as in the solder cracking test except that each glass epoxy substrate was placed in an environment in which the thermal shock cycle was repeated 1000 cycles, 2000 cycles, and 3000 cycles.
Next, the target portion of each test substrate was cut out and sealed with an epoxy resin (product name: epocount (main agent and curing agent), manufactured by Refine Tec ltd. Further, the central cross section of the QFP part mounted on each test substrate was observed by a wet grinder (product name: Tegrapol-25, manufactured by Marumoto struts K.K.), and whether or not the crack generated in the solder joint completely intersected the solder joint and broke was observed by a scanning electron microscope (product name: TM-1000, manufactured by Hitachi High-technologies corporation), and the crack generated in the solder base material and the crack generated at the interface (intermetallic compound) between the solder joint and the lead of the QFP part were evaluated as follows. The results are shown in tables 6 to 10. The number of QFPs evaluated in each thermal shock cycle was set to 20, 8 leads at 4 corners of each 1 QFP were observed, and the cross section of 160 leads in total was confirmed.
Cracks generated in the solder base material
◎ No crack completely crossing the solder base material occurred up to 3000 cycles
○ cracks completely crossing the solder base material between 2001 and 3000 cycles
△ cracks completely crossing the solder base material between 1001 and 2000 cycles
X: crack generated when the number of cycles is less than 1000
Cracks generated at the interface between the solder joint and the lead of the QFP part
◎ No cracks were generated across the interface completely up to 3000 cycles
○ cracks completely crossing the interface between 2001 and 3000 cycles
△ cracks completely crossing the interface between 1001 and 2000 cycles
X: crack formation across the interface at less than 1000 cycles
(4) Solder cracking test in Sn-plated SON
1.3mm pitch SON (Small outline leadless-leaded package) components (terminal count 8 pins, product name: STL60N3LLH5, manufactured by STMicroelectronics corporation) having dimensions of 6mm × 5mm × 0.8 tm; each test substrate was fabricated under the same conditions as the solder cracking test in the Sn plating QFP except that the test substrate was provided with a solder resist having a pattern capable of mounting the SON component, a glass epoxy substrate for connecting electrodes (according to the manufacturer's recommended design) of the SON component, and a metal mask having the same pattern and a thickness of 150 μm, and whether or not the crack generated in the solder joint completely intersected the solder joint and broke was observed using a scanning electron microscope (product name: TM-1000, manufactured by High-Technologies Corporation). Based on this observation, cracks occurring in the solder base material and cracks occurring at (intermetallic compounds of) the interface between the solder joint and the electrode of the SON component were classified and evaluated as follows. The results are shown in tables 6 to 10. Note that the number of evaluated SON in each thermal shock cycle was set to 20, 1 terminal of the gate electrode was observed for each 1 SON, and the cross section of 20 terminals in total was confirmed.
Cracks generated in the solder base material
◎ No crack completely crossing the solder base material occurred up to 3000 cycles
○ cracks completely crossing the solder base material between 2001 and 3000 cycles
△ cracks completely crossing the solder base material between 1001 and 2000 cycles
X: crack generation at less than 1000 cycles
Cracks at the interface of the solder joint and the electrode of the SON component
◎ No cracks were generated across the interface completely up to 3000 cycles
○ cracks completely crossing the interface between 2001 and 3000 cycles
△ cracks completely crossing the interface between 1001 and 2000 cycles
X: crack formation across the interface at less than 1000 cycles
(5) Liquidus measurement
For each of the lead-free solder alloys of examples and comparative examples, the liquidus temperature was measured using a differential scanning calorimetry apparatus (product name: EXSTAR DSC6200, Seiko Instruments Inc.). The measurement conditions were as follows: the temperature rise rate was 10 ℃/min at room temperature to 150 ℃ and 2 ℃/min at 150 ℃ to 250 ℃, and the sample amount was 10 mg. The results are shown in tables 6 to 10.
(6) Void test
Each test substrate was prepared by mounting chip components on each glass epoxy substrate under the same conditions as in the solder cracking test. Then, the surface state of each test substrate was observed using an X-ray transmission device (product name: SMX-160E, manufactured by Shimadzu corporation), and the ratio of the total area occupied by the voids in the region where the solder joint was formed (the area ratio of the voids) was measured. The occurrence of voids was evaluated as follows by obtaining an average value of the area ratio of voids in the pad at 40 points in each test substrate. The results are shown in tables 6 to 10.
◎ the average value of the area ratio of voids is 3% or less and the effect of suppressing the generation of voids is extremely good
○ has an average value of void area ratio of more than 3% and not more than 5%, and has a good effect of suppressing void generation
△ has an average value of void area ratio of more than 5% and not more than 10%, and has a sufficient effect of suppressing void formation
X: the average value of the area ratio of voids is more than 10% and 15% or less, and the effect of suppressing the generation of voids is insufficient
(8) Copper corrosion test
FR4 substrate having a copper wiring thickness of 35 μm was cut into an appropriate size. Then, a pre-flux was applied to the copper wiring surface, and the copper wiring surface was preheated for 60 seconds so that the temperature of the test substrate was about 120 ℃. Next, a jet solder bath in which each lead-free solder alloy of examples and comparative examples was melted was prepared, and each test substrate was placed 2mm above the jet opening of the jet solder bath and immersed in the molten solder for 3 seconds. This dipping step was repeated, and the number of times of dipping until the size of the copper wiring of each test substrate was halved was measured and evaluated as follows. The results are shown in tables 6 to 10.
○ the size of the copper wiring is not halved even if the immersion is performed 4 times or more.
X: when the immersion was performed 3 times or less, the size of the copper wiring was reduced by half.
[ Table 6]
[ Table 7]
[ Table 8]
[ Table 9]
[ Table 10]
As described above, even in the case of the electronic component using the Sn plating layer, the solder joint formed using the lead-free solder alloy of the example can suppress the progress of cracks and the electrode peeling phenomenon of the electronic component due to the solder joint even in a severe environment such as a large temperature difference between cold and warm temperatures and load vibration. Even when 3.0 wt% or less of Bi is added, the effects of suppressing the progress of cracks and the electrode peeling phenomenon can be exhibited without inhibiting the stretchability.
In particular, lead-free solder alloys containing In can be reduced In liquidus line without inhibiting the effects of suppressing the progress of cracks and suppressing the electrode separation phenomenon.
Therefore, the electronic circuit board having such solder joints can be suitably used as an electronic circuit board requiring high reliability, such as a vehicle-mounted electronic circuit board. Further, such an electronic circuit board can be suitably used for an electronic control device which requires further higher reliability.
Claims (10)
1. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 or 0.9 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% of Ni and Co in total, 0.5 to 3 wt% of Bi, and Sn as the main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
2. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 or 0.9 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% of Ni and Co In total, 0.5 to 3 wt% of Bi, 6 to 6 wt% of In, and Sn as a main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
3. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 or 0.9 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% in total of Ni and Co, 0.5 to 3 wt% of Bi, at least 1 of Ga and Ge in total of 0.001 to 0.05 wt% and Sn as a main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
4. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 or 0.9 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% In total of Ni and Co, 0.5 to 3 wt% of Bi, 6 to In, 0.001 to 0.05 wt% In total of at least 1 of Ga and Ge, and Sn as a main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
5. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 or 0.9 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% in total of Ni and Co, 0.5 to 3 wt% of Bi, 0.001 to 0.05 wt% in total of at least 1 of Fe, Mn, Cr and Mo, and Sn as a main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
6. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% In total of Ni and Co, 0.5 to 3 wt% of Bi, 6 to In, 0.001 to 0.05 wt% In total of at least 1 of Fe, Mn, Cr and Mo, and Sn as a main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
7. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 or 0.9 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% in total of Ni and Co, 0.5 to 3 wt% of Bi, 0.001 to 0.05 wt% in total of at least 1 of Ga and Ge, 0.001 to 0.05 wt% in total of at least 1 of Fe, Mn, Cr and Mo, and Sn as a main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
8. A lead-free solder alloy is characterized by consisting of only 1 to 4 wt% of Ag, 0.5 or 0.9 to 1 wt% of Cu, 1 to 5 wt% of Sb, 0.1 to 0.25 wt% In total of Ni and Co, 0.5 to 3 wt% of Bi, 6 wt% In, 0.001 to 0.05 wt% In total of at least 1 of Ga and Ge, 0.001 to 0.05 wt% In total of at least 1 of Fe, Mn, Cr and Mo, and Sn as a main component,
wherein Ni is contained in an amount of 0.05 wt% or more and Co is contained in an amount of 0.05 wt% or more.
9. An electronic circuit board characterized by having a solder joint formed using the lead-free solder alloy according to any one of claims 1 to 8.
10. An electronic control device comprising the electronic circuit board according to claim 9.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
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| JP2015-061792 | 2015-03-24 | ||
| JP2015061792 | 2015-03-24 | ||
| JP2016-038976 | 2016-03-01 | ||
| JP2016038976A JP6200534B2 (en) | 2015-03-24 | 2016-03-01 | Lead-free solder alloy, electronic circuit board and electronic control device |
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| CN106001978A CN106001978A (en) | 2016-10-12 |
| CN106001978B true CN106001978B (en) | 2020-02-07 |
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| KR102447392B1 (en) | 2015-05-05 | 2022-09-27 | 인듐 코포레이션 | Lead Free Solder Alloys for Electronic Applications |
| CN107427968B (en) | 2015-09-17 | 2020-11-24 | 富士电机株式会社 | Solder material for semiconductor device |
| MX2018011176A (en) | 2016-03-22 | 2019-03-28 | Tamura Seisakusho Kk | Lead-free solder alloy, flux composition, solder paste composition, electronic circuit board and electronic control device. |
| JP6230737B1 (en) * | 2017-03-10 | 2017-11-15 | 株式会社タムラ製作所 | Lead-free solder alloy, solder paste and electronic circuit board |
| HRP20211378T1 (en) * | 2017-03-31 | 2021-12-24 | Senju Metal Industry Co., Ltd | Solder alloy, solder paste, and solder joint |
| US10456872B2 (en) * | 2017-09-08 | 2019-10-29 | Tamura Corporation | Lead-free solder alloy, electronic circuit substrate, and electronic device |
| CA3054395A1 (en) * | 2017-09-14 | 2019-03-21 | Tamura Corporation | Lead-free solder alloy, electronic circuit substrate, and electronic control device |
| CN109500510A (en) * | 2017-09-14 | 2019-03-22 | 株式会社田村制作所 | Lead-free solder alloy, electronic circuit board and electronic control unit |
| JP6292342B1 (en) * | 2017-09-20 | 2018-03-14 | 千住金属工業株式会社 | Solder alloy for joining Cu pipe and / or Fe pipe, preform solder, cored solder and solder joint |
| JP7133397B2 (en) * | 2017-09-27 | 2022-09-08 | 株式会社タムラ製作所 | Lead-free solder alloy, electronic circuit board and electronic control device |
| JP6349615B1 (en) | 2017-10-03 | 2018-07-04 | 株式会社弘輝 | Solder alloy, solder joint material and electronic circuit board |
| US11732330B2 (en) * | 2017-11-09 | 2023-08-22 | Alpha Assembly Solutions, Inc. | High reliability lead-free solder alloy for electronic applications in extreme environments |
| US11577343B2 (en) | 2017-11-09 | 2023-02-14 | Alpha Assembly Solutions Inc. | Low-silver alternative to standard SAC alloys for high reliability applications |
| CN108611522B (en) * | 2018-05-03 | 2020-05-26 | 绍兴市天龙锡材有限公司 | Tin alloy wire |
| CN108857143A (en) * | 2018-08-16 | 2018-11-23 | 铜山县恒丰机械有限公司 | A kind of mechanical welding material powder material |
| DE102018123924A1 (en) | 2018-09-27 | 2020-04-02 | Infineon Technologies Ag | A semiconductor device with a solder joint having a Sn / Sb connection |
| CN108994480A (en) * | 2018-10-10 | 2018-12-14 | 云南锡业锡材有限公司 | A kind of SnBiAgCu high-reliability lead-free solder alloy |
| JP6731034B2 (en) * | 2018-12-25 | 2020-07-29 | 株式会社タムラ製作所 | Lead-free solder alloy, solder joint material, electronic circuit mounting board and electronic control device |
| WO2020176583A1 (en) * | 2019-02-26 | 2020-09-03 | Indium Corporation | High reliability leadfree solder alloys for harsh service conditions |
| CN111660037B (en) * | 2019-03-05 | 2022-04-15 | 潮州三环（集团）股份有限公司 | Soldering flux and solder paste containing same |
| JP6624322B1 (en) | 2019-03-27 | 2019-12-25 | 千住金属工業株式会社 | Solder alloy, solder ball, solder preform, solder paste and solder joint |
| JP6700568B1 (en) * | 2019-08-09 | 2020-05-27 | 千住金属工業株式会社 | Lead-free and antimony-free solder alloys, solder balls, ball grid arrays and solder joints |
| JP7068370B2 (en) * | 2020-03-19 | 2022-05-16 | 千住金属工業株式会社 | Solder alloys, solder balls and solder fittings |
| JP6889387B1 (en) | 2020-06-23 | 2021-06-18 | 千住金属工業株式会社 | Solder alloys, solder pastes, solder balls, solder preforms, solder joints, in-vehicle electronic circuits, ECU electronic circuits, in-vehicle electronic circuit devices, and ECU electronic circuit devices |
| JP6836040B1 (en) | 2020-07-31 | 2021-02-24 | 千住金属工業株式会社 | Solder alloy |
| JP2024526066A (en) * | 2021-06-11 | 2024-07-17 | インディウム コーポレーション | Highly reliable lead-free solder paste using mixed solder alloy powder |
| KR20240110906A (en) * | 2021-11-30 | 2024-07-16 | 가부시키가이샤 다무라 세이사쿠쇼 | Solder alloys, solder joints, solder pastes and semiconductor packages |
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| WO2014163167A1 (en) * | 2013-04-02 | 2014-10-09 | 千住金属工業株式会社 | Lead-free solder alloy and in-vehicle electronic circuit |
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